Roles of Blue-shifted Hydrogen Bond C-H・・・O in Aqueous Micell Solutions

2005 Fiscal Year Final Research Report Summary

• Project/Area Number: 16550010
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Physical chemistry
• Research Institution: University of Fukui
• Principal Investigator: MIZUNO Kazuko University of Fukui, Faculty of Engineering, Department of Applied Chemistry and Biotechnology, Associate Professor, 工学部, 助教授 (10126641)
• Project Period (FY): 2004 – 2005
• Keywords: Blue-shifted hydrogen bond / C-H・・・OH_2 / Ethylene oxide chain / Hydration of CH group / IR / Depolarization of water / Bi-functional hydrogen bonds

Research Abstract

Infrared and Raman studies have been carried out for aqueous binary mixtures of CH_3-(OCH_2CH_2)_n-OCH_3 [I], where n=1, 2, and 4. D_2O and H_2O mixtures (95:5 in volume) were used instead of H_2O in order to observe spectra changes in the C-H vibration bands quantitatively. The changes in the molecular structures of the solutes on mixing with water was probed by the wavenumbers of the C-O stretching vibration band of the ether oxygens, C-H stretching vibration bands, and their absorption intensities in the IR spectra. The changes in the polarization of the water molecules were probed by the wavenumber of the O-H vibration bands of HOD. Continuous red-shifts of the C-O band were observed for the three solutes with increasing water concentration, showing that hydrogen-bonding interaction becomes stronger with increasing water concentration. Blue-shifts and decreases in absorption intensities of the C-H bands were observed with increasing water concentrations, showing the formation of blue-shifted hydrogen bonds C-H・・・OH_2 definitely. The wavenumber of the O-H band probing the hydrogen-bonding strength of the water decreased at the lowest concentrations of the solutes, and then increased inversely with increasing the solute concentrations. The results indicate the formation of hydration clusters at the lowest concentrations of the solutes, but the hydrogen-bonding strength of the water decreases with increasing the solute concentrations. The results demonstrate that so called iceberg structure is not formed in the mixtures, but the polarization of the water decreases with increasing the solutes. All these results show that blue-shifted C-H・・・OH_2 hydrogen bondings and >C-O・・・HOH occur simultaneously. We conclude that the formation of such the bi-functional hydrogen bonds >C-O・・・H(H)O・・・H-C are the origin of the hydration of the CH groups in ethylene oxide chains.